Ngspice cheatsheet
Ming Sun / November 04, 2022
4 min read • ––– views
Operating point
Usage: DC operating point simulation.
name=SPICE only_toplevel=false value="
.op
.save all
"
DC sweep with Xschem and Ngspice
Usage: Sweep Vin from 0V to 1.8V with 1mV per step.
name=SPICE only_toplevel=false value="
.dc Vin 0 1.8 0.001
.save all
"
Transient sim with Xschem and Ngspice
Usage: 1µs transient simulation with 0.01ns step size.
name=SPICE only_toplevel=false value="
.tran 10p 20n
.save all
"
Voltage pulse with Xschem and Ngspice
Usage: 0V~1.8V, 1ns delay time, 1ns rise time, 1ns fall time, 4ns duration, 10ns period.
name=Vin
value="pulse(0 1.8 1ns 1ns 1ns 4ns 10ns)"
Write simulation result to *.raw file
Usage: write simulation result to *.raw file for waveform viewer.
name=NGSPICE
only_toplevel=true
value="
.control
save all
tran 100p 2u
write SIM_nand2.raw
set appendwrite
.endc
"
Load/unload simulation data
Usage: right click to load/unload simulation data.
Symbol: devices/launcher.sym
name=h1
descr="Select arrow and
Ctrl-Left-Click to load/unload
simulation .raw file"
tclcommand="
xschem raw_read $netlist_dir/[file tail [file rootname [xschem get current_name]]].raw
"
Automatic plot in Ngspice
Usage: automatic plot in Ngspice after the simulation is done.
name=NGSPICE
only_toplevel=true
value="
.control
save all
tran 10n 6u
plot g g2
write test_mim_cap.raw
.endc
"
PWL (piece wise linear) current
name=I2 value="pwl 0 0 1p 100n"
Simple diode spice model[3]
IS: saturation current VJ: junction potential
.model diode D (IS=1e-12 VJ=0.7)
Simple switch model with hysteresis[4]
Ron: on impedance Roff: off impedance Vt: turn on threshold Vh: hysteresis
.model switch SW(Ron=1m Roff=1G Vt=1.2 Vh=0.2)
References and materials
[1] Ngspice website